var collection = new ServiceCollection();

collection.Scan(scan => scan
     // We start out with all types in the assembly of ITransientService
    .FromAssemblyOf<ITransientService>()
        // AddClasses starts out with all public, non-abstract types in this assembly.
        // These types are then filtered by the delegate passed to the method.
        // In this case, we filter out only the classes that are assignable to ITransientService
        .AddClasses(classes => classes.AssignableTo<ITransientService>())
            // Whe then specify what type we want to register these classes as.
            // In this case, we wan to register the types as all of its implemented interfaces.
            // So if a type implements 3 interfaces; A, B, C, we'd end up with three separate registrations.
            .AsImplementedInterfaces()
            // And lastly, we specify the lifetime of these registrations.
            .WithTransientLifetime()
        // Here we start again, with a new full set of classes from the assembly above.
        // This time, filtering out only the classes assignable to IScopedService.
        .AddClasses(classes => classes.AssignableTo<IScopedService>())
            // Now, we just want to register these types as a single interface, IScopedService.
            .As<IScopedService>()
            // And again, just specify the lifetime.
            .WithScopedLifetime());

var collection = new ServiceCollection();

// First, add our service to the collection.
collection.AddSingleton<IDecoratedService, Decorated>();

// Then, decorate Decorated with the Decorator type.
collection.Decorate<IDecoratedService, Decorator>();

// Finally, decorate Decorator with the OtherDecorator type.
// As you can see, OtherDecorator requires a separate service, IService. We can get that from the provider argument.
collection.Decorate<IDecoratedService>((inner, provider) => new OtherDecorator(inner, provider.GetRequiredService<IService>()));

var serviceProvider = collection.BuildServiceProvider();

// When we resolve the IDecoratedService service, we'll get the following structure:
// OtherDecorator -> Decorator -> Decorated
var instance = serviceProvider.GetRequiredService<IDecoratedService>();